According to a known seat apparatus for a vehicle, left and right lower arms, which are attached to a seat cushion, are provided on a vehicle floor. Left and right upper arms, which are attached to a seat back, are supported by back portions of the corresponding lower arms so as to pivot about corresponding hinge pins. A left reclining mechanism is provided between the left lower arm and the left upper arm. Likewise, a right reclining mechanism is provided between the right lower arm and the right upper arm. The left and right reclining mechanisms restrict pivotal movements of the corresponding upper arms and release the restriction of the pivotal movement thereof.
A known seat reclining apparatus for a vehicle disclosed in JP2006-333967A (which is hereinbelow referred to as reference 1) includes the left and right reclining mechanisms respectively provided at left and right sides of the seat cushion in order to obtain a supporting strength of the seat back. In such structured seat reclining apparatus for a vehicle, when a seat back angle is adjusted, the left and right reclining mechanisms are operated synchronously to lock and unlock the pivotal movements of the corresponding upper arms. In order to synchronize operations of the left and right reclining mechanisms, the reclining mechanisms are connected to each other through a pipe-shaped connecting shaft.
According to the seat reclining apparatus disclosed in reference 1, left and right operating shafts are respectively inserted into the left and right reclining mechanisms from an outward of a vehicle seat. An end portion of the left operating shaft and that of the right operating shaft are respectively connected to left and right end portions of the pipe-shaped connecting shaft via welding portions 22. Cams are engaged with the corresponding operating shafts. First teeth portions are formed at outer surfaces of lock members. Second teeth portions are formed at inner surfaces of rotating members. The first teeth portions are engaged with and released from the corresponding second teeth portions by means of a rotational movement of the cam. When an operating knob provided at an end potion of either left or right operating shaft, is operated, the left and right reclining mechanisms synchronously perform locking and unlocking operations.
However, according to the seat reclining apparatus (for the vehicle) disclosed in reference 1, the left and right operating shafts are respectively inserted into the left and right reclining mechanisms from the outward of the vehicle seat before the operating shafts and the connecting shaft are connected by welding. Therefore, the operating shafts and the connecting shaft are connected by welding in a state where the operating shafts are not stably positioned. As a result, the operating shafts may be eccentrically connected to the connecting shaft. Then, the locking and unlocking operations of the lock mechanisms may malfunction. Further, the seat reclining apparatus for the vehicle according to reference 1 does not include clearances, which are provided between the left reclining mechanism and the left operating shaft and between the right reclining mechanism and the right operating shaft, and which offset positional variations between the left and right reclining mechanisms. Therefore, the locking and unlocking operations of the lock mechanisms may further malfunction.
A need thus exists for a seat reclining apparatus for a vehicle which is not susceptible to the drawback mentioned above.